I'm finally getting around to changing the back wheel that has a bad wobble it has only been 40 years.I found a good almost true rim in my parts stash but it has some major rust pits on the inside of the rim.I see coker sells flaps that cover the entire inside of the rim giving you a nice smooth surface for the tube to sit on,I'm wondering if any one has tried a flap in the rim before i order one,the rim is 21 inch.